I've participated in many such charity fun runs and see no problem with this type of arrangement. It takes a lot of work and experience to host successful running events: registration, insurance, web site development, course marking, permits, aid stations, timing, t-shirts, clean up, etc. It's worth paying an event management company to ensure everything runs smoothly. Shop around and you might find a smaller local company willing to do it for a lower price.
In the end the charity still gets more money than they had before and the runners get some exercise: win / win. Plus you've raised awareness of the cause and some participants will go on the become regular donors.
In the end the charity still gets more money than they had before and the runners get some exercise: win / win. Plus you've raised awareness of the cause and some participants will go on the become regular donors.